Construction of super-hydrophobic hypercrosslinked porous polymers for selectively removing aromatic diamines from the polyurethane bio-hydrolysate

Abstract The upcycling of Polyurethane (PU) degradation products has been gaining tremendous attention and research interest in recent years. In particular, due to the toxicity to microorganisms, the key process is to remove aromatic diamines selectively and efficiently from the bio-hydrolysate which also includes multiple carboxylic diacids and polyols. Herein, a series of super-hydrophobic hypercrosslinked porous polymers (HCPPs) were prepared to selectively remove aromatic diamines in a neutral condition. They were facially fabricated via Friedel-Crafts alkylation reactions with benzene and three types of benzyl bromides. Besides, the surface area, porous structure, and hydrophobic properties of resulting polymers were adjusted by changing the length and connected nodes numbers of crosslinkers. Particularly, HCPP-TBMB knitted by 1,3,5-tris(bromomethyl)-benzene (TBMB) owned a maximum BET surface area of 1048.8 m2 g−1 with hierarchical porosity, as well as high thermal stability and super-hydrophobicity. The adsorption experiments on HCPP-TBMB clarified the large adsorption capacities of 2,4-toluene diamine (TDA, 1.062 mmol g−1) and 4,4′-methylene dianiline (MDA, 1.971 mmol g−1) as well as high selectivity in the model PU hydrolysate. Moreover, thermodynamic experiments and spectral analysis revealed the physical adsorption process for uptake of aromatic diamines on HCPP-TBMB. The main adsorption mechanism contained π-π stacking, hydrophobic interaction, and hole size effect. These findings may provide a promising strategy for highly selective removal of aromatic diamines from the PU bio-hydrolysate.